Colour by Design - Organic Mechanisms
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draw an example mechanism for electrophilic addition
describe the process of electrophilic addition
a pair of electrons from the double bond attacks an electrophile to form a new bond the other carbon in the double bond is now a carbocation a nucleophile attacks the carbocation to form a bond
what type of mechanism is alkenes reacting with bromine?
electrophilic addition
what are the reaction conditions for the reaction between alkenes and bromine?
H in presence of a catalyst to form an alkane -> Ni + heat + pressure or Pt + RTP water in presence of catalyst to give alcohol -> conc sulfuric then add steam
draw an example mechanism for nucleophilic substitution
what is a nucleophile?
a molecule with a lone pair of electrons that it can donate to form a dative covalent bond
describe the process of nucleophilic substitution
nucleophile attacks carbon deficient atom in C-X bond nucleophile donates 2 electrons to form dative covalent bond C-X bond breaks heterolytically and X recieves 2 electrons, leaving compound as X-
describe heterolytic bond breaking
both electrons from bond goes to one atom one positive and one negative ion produced
describe homolytic bond breaking
each atom gets 1 electron from bond breaking 2 radicals produced
what is a radical?
a species with an unpaired electron
what are the 3 steps in radical reactions?
initiation propogation termination
what happens during the initiation step in a radical reaction?
one or more molecules react to form radicals a bond breaks by homolytic fission often in presence of UV light
what happens during the propogation steps of radical reactions?
molecule and radical react to form new molecule or radical pair bond breaks and new bond forms usually occurs in pairs - one step produces intermediate that then reacts in second step
what happens during termination steps in radical reactions?
2 radicals react to form one molecule bonds form so exothermic
what is the functional group of a cyano compound?
N≡C-
what can cyano groups also be known as?
nitrile groups
are nitriles electophilic or nucleophilic?
nucleophilic
draw an example mechanism of nucleophilic addition
where does the hydrogen ion come from in nucleophilic addition?
acidic conditions
what are the products of nucleophilic addition involving cyano groups called?
cyanohydrins
what are cyanohydrins?
a molecule with a cyano group and hydroxy group on the same carbon
what happens when haloalkanes react with HCN?
halogen acts similar to O in nucleophilic addition if halogen is a good leaving group - nucleophilic substitution, if not - nucleophilic addition
why won’t benzene undergo electrophilic addition?
in order to go through mechanism - delocalisation would have to be broken as double bonds aren’t fixed around molecule
draw a general mechanism for the electrophilic substitution of arenes
